This amended proposal is for a K01 Mentored Research Scientist Development Award. The applicant is an epidemiologist and developing investigator at the Yale School of Medicine. Her goal is to become an expert and leader in the epidemiology of aging at the interface of psychosocial epidemiology and functional status. Her approach to achieving this goal is to learn advanced statistical methodology to elucidate the relationship between depression and disability over time in light of the emerging paradigm of disability as dynamic and highly complex. The proposed training and research plans are designed to complement and reinforce one another. The specific training objectives are to (1) acquire expertise in the epidemiology of disability and depression and obtain new skills in primary data collection; (2) develop expertise in the analysis of complex longitudinal data; (3) develop and refine a set of survival skills that are critical for a successful career as an independent investigator (e.g., grant writing); and (4) enhance her knowledge base regarding innovative research in aging. A secondary goal is to gain hands-on knowledge of the development and implementation of clinical trials research. The proposed research is designed to rigorously evaluate the reciprocal nature of the relationship between depression and disability, operationalized as disability burden and clinically-meaningful subtypes. Additionally, the applicant proposes to systematically determining the mechanisms that underlie the reciprocal relationship between depression and disability, and to evaluate if this relationship differs according to gender. The research will be conducted using data from the Yale PEP (Precipitating Events Project) Study, an ongoing NIA-funded, longitudinal study of 754 initially non-disabled community-living older persons. The conceptual and methodological challenges of using these data to test hypotheses directed at determining if a feedback loop exists between depression and disability over time will reinforce the applicant's formal training. Research that improves our understanding of how depression influences the complex trajectory of disability is highly significant to the field of aging; it will highlight a factor that, if adequately identified and managed, could help to prevent the development and progression of disability. Alternately, improving our understanding of this relationship may help to identify opportunities to prevent the development and progression of depression.